Federal aviation regulations require supplemental oxygen for those flying at 12,500 feet or higher for 30 minutes or longer in a nonpressurized aircraft. At altitudes above 14,000 feet, pilots must use oxygen at all times. Above 15,000 feet, all occupants must be provided oxygen.
Without supplemental oxygen, the human body begins to decline quickly above 26,000 feet.
In the two minutes after the explosion, Southwest 1380 plunged about 8,000 feet, to about 24,600. Within the next five minutes, the aircraft descended to about 11,000 feet. It was on the ground about 10 minutes later.
Former flight attendants said that Flight 1380 underscored the importance of the safety instructions delivered to passengers as the planes taxi to the runway. But it also revealed what many flight attendants already know: Passengers tune them out.
“They probably didn’t pay attention to the emergency instructions,” Marguerite Bartlett, an American Airlines flight attendant in the 1960s, said in an interview. “I have been on many, many flights as a passenger, and an awful lot of do not pay attention.”
Mr. Bourman, who flies three or four times a year, acknowledged that over time, he began tuning out the safety instructions but that that would not be the case going forward. “Next time I’m on a plane — it’s not going to be for a while, when I get the guts to get back on — I will listen,” he said.
“The only way you’re going to get people to do it is to scare the crap out of them,” he added.
During her five years as a flight attendant, Ms. Bartlett said, the oxygen masks never dropped during an emergency. But one flight that landed in Cincinnati skidded off the runway during a snowstorm.
In that moment, she said, it was clear the passengers had not remembered what to do.
“Everybody got out safely, but they really didn’t know the instructions,” she said, adding that she had to remind each passenger what to do in an emergency.
For years, a flight attendant recited safety instructions over a loudspeaker, while another walked the aisle and demonstrated how to fasten a seatbelt or inflate a life vest. In recent years, the in-person instructions have been replaced with splashy, choreographed videos.
When Grayce Schor started as a flight attendant in the 1970s for American Airlines, she would demonstrate for passengers how to tighten an oxygen mask if there was an emergency. But not once in her 35 years as a flight attendant were the oxygen masks needed in flight, she said.
“It’s not a big mask,” Ms. Schor, who retired from American Airlines in 2006, said in an interview, but “it is supposed to be around your nose and mouth.”
When Ms. Schor saw a photo from the Southwest Airlines flight on Tuesday, however, she shrugged off the passengers’ mistakes.
“I wouldn’t make a big deal,” she said. “They are still going to get the oxygen through your mouth.”